In modern hospitals, there is a trend towards implementation of so-called rapid response systems. A rapid response system identifies deteriorating patients in general wards before the deterioration has become too profound. Upon detection of a deteriorating patient, the respective patient is assessed by a rapid response team to prevent further deterioration, admission to the intensive care unit (ICU), and even death.
Since early deterioration of patients can be observed from changes in the patient's vital signs, it becomes more and more common that vital signs of patients in general wards of hospitals are monitored such that a rapid response team can intervene rapidly when deteriorations are detected. In this way adverse outcomes can be prevented. While the four vital signs heart rate, blood pressure, respiration rate, and temperature can be automatically measured and monitored by means of well known medical sensors, the level of consciousness being a fifth vital sign has commonly to be determined manually by care personnel. It should be noted that the respiration rate is considered the most important parameter and the level of consciousness is considered the second most important parameter for detecting a decline in patient condition in hospitals.
In this context, the term consciousness means the ability of an individual to respond appropriately to environmental stimuli. Loss of this ability is generally judged as an alteration of consciousness. There are two major aspects of consciousness: on the one hand arousability, namely whether the individual responds to external stimuli, and on the other hand the appropriateness of the content of the consciousness, namely whether the response to stimuli, in particular stimuli requiring contextual response (such as for instance the answer to the question “What is your name”), is within the appropriate context.
Conventionally, the level of consciousness of patients is assessed by doctors, nurses, or other health care professional in terms of the responsiveness to the environment. Various methods and scales have been developed to assess and quantify the level of consciousness. The Glasgow Coma Scale (GCS) is the most widely used scoring system in quantifying the level of consciousness of patients following traumatic brain injury. The GCS quantifies the verbal, motor, and eye-opening responses to verbal and pain stimulation separately. Each type of response is scored, on the scale of 1 to 4, 1 to 5, and 1 to 6, respectively, depending on the type of responses. A lower score means a more decreased level of consciousness. The scores of each response are added into a final score on a scale of 3-15.
Further, the so-called AVPU scale which is a simplification of the GCS scale is also commonly used. In the AVPU scale there are only four possible outcomes which are assessed from the best eye, voice, and movement responses to the stimuli. According to this scale, “Alert” signifies a state in which the patient is fully awake, shows spontaneous eye opening, responds to voice, and has bodily motor function; “Voice” signifies a state in which the patient is not fully awake but responds to the assessor's voice; “Pain” signifies a state in which the patient does not respond to voice but responds to a painful stimulus administered, such as a fingernail press by the assessor; and “Unconscious” signifies a state in which the patient does not respond to pain. According to the AVPU scale the first characters “A”, “V”, “P”, and “U” of the states are also used as abbreviations for the respective states. In clinical practice, the AVPU scale is commonly used for rapid assessment of acutely ill patients. Further, because it is a simpler tool as compared to the GCS scale, it has also been incorporated into many early warning score systems.
The assessment of consciousness according to the above described methods is based on a fairly subjective manual task and is commonly performed in hospitals in periodic spot check manner, typically every 8 hours.
As has been pointed out above, there is a demand for automated consciousness detection.
U.S. Pat. No. 6,416,480 B1 describes a system and a method for computerized automated acquisition of the Glasgow Coma Score (GCS) for quantifying the level of consciousness following traumatic brain injury. The system is intended to be used in medical units such as intensive care units, emergency rooms, and operating rooms. The assessment of critically ill patients is performed on a periodic basis based on stimulus-induced standard physiological and verbal responses of the patient. The system aims at providing a coma score which corresponds one-to-one with the GCS as obtained by human assessors. Such an automated system comprises the following advantages: (1) it does not introduce a subjective bias based upon previous assessments, as may commonly occur when nurses and physicians assess the GCS; (2) it eliminates the errors often made by the nurses or physicians while recording the GCS on paper or entering it into a computerized system by hand; (3) it may offer significant savings in personnel costs at the hospital intensive care units, emergency rooms, neurology/neuroscience wards and other sites where the level of consciousness of patients needs to be evaluated at regular intervals; (4) it permits more frequent assessment and thus a more rapid response to changes in the patient's status, thereby potentially saving lives as well as decreasing or preventing brain damage. However, the described system also comprises some disadvantages, namely: In every cycle of the GCS assessment, at least two verbal stimulations are necessary for assessing the highest scores of verbal and motor response. The frequent GCS assessments will potentially annoy the patients which may lead to patients ignoring the stimulation. However, since ignoring the stimulation may lead to even more unpleasant stimulation (pain stimulation), the patient may consequently try to remove the stimulators altogether. Further, in order to achieve the GCS results, the described system exploits measurement and detection methods which are invasive and impractical for applications in general wards.
Although in some cases a detailed assessment of the level of consciousness is required which legitimates a detailed analysis involving high costs and discomfort for the patient, there is a demand for an easy way of answering the question whether a patient is in state of full consciousness or not. In particular, there is a demand for an automatic procedure and system for monitoring consciousness of patients in general wards of hospitals (i.e. not in the intensive care unit (ICU) or in the emergency room (ER)). Further, it has been found that periodic and deliberate stimulations are potentially annoying and uncomfortable to the patients. Such annoyance can result in non-compliance behavior of the patients.